1. Field of the Invention
The present invention relates generally to printing inks and, more particularly, but not by way of limitation, to a vegetable oil-based printing ink for lithographic printing presses.
In one aspect, the present invention relates to a method of reclaiming residual vegetable oil-based printing ink from a printing press during the cleaning of a printing press by recovering residual vegetable oil-based printing ink from printing presses and utilizing such recovered residual vegetable oil-based printing ink in the formulation of the vegetable oil-based printing ink.
In another aspect, the present invention relates to a method for polymerizing a vegetable oil component of such vegetable oil-based printing ink.
2. Brief Description of the Prior Art
Printing ink produced in the past has been petroleum-based, typically comprised of 15-20% carbon black as the pigment, 15-25% hydrocarbon or alkyd resin, and 50-70% mineral oil solvent. Nearly 500 million kilograms of inks for these applications are produced domestically each year. This volume of production represents a substantial consumption of petroleum-based ingredients. The petroleum oil shortage in the mid-1970""s stimulated research to find alternatives to mineral oil and other petroleum products in ink formulations.
In the early 1980""s, the American Newspaper Publishers Association (xe2x80x9cANPAxe2x80x9d) directed a research effort on developing a non-petroleum-based vehicle for newspaper inks. In response to the ANPA directives, numerous approaches were taken resulting in the formulation of vegetable oil-based ink using a combination of petroleum based ingredients and soy bean oil. Widespread commercial acceptance of the petroleum based/soy bean oil ink has been inhibited, however, by the cost, which is 50-70% more than traditional petroleum-based black inks. Additionally, although these inks tout the 100% soy bean oil ingredient, petroleum derivatives are still added to the formulation of the ink to achieve certain characteristic standards.
Despite these advances made by the ANPA and others, the industry has continued to seek a non-petroleum-based printing ink which would xe2x80x9c(1) be cost competitive with petroleum-based inks; (2) not require any petroleum-derived component; (3) resist ruboff on hands and clothing; and (4) enable formulation over a wide range of viscosities required by various printing applications.
In 1991, U.S. Pat. No. 5,122,188 was granted wherein Nitrogen was employed to produce a 100% vegetable oil-based printing ink with no petroleum derivatives. Problems have been encountered in employing the non-petroleum derivatives when scaling up for commercialization of the process. The problems that persist in the use of vegetable oil-based inks for lithographic printing presses include lengthy drying time, environmental waste concerns, high production costs, difficulty in clean up, and high material costs.
The present invention solves the above problems that exist in prior vegetable oil-based printing inks by providing a vegetable oil-based printing ink system that lowers material and production costs. Additionally, the vegetable oil-based printing ink is recyclable and removable directly from the printing presses for reuse as a component in the formulation of the vegetable oil-based printing ink. A significant benefit in the current invention is the ability to polymerize vegetable oil in the same process to form high quality recyclable vegetable oil-based printing inks having a wide range of viscosities. The vegetable oil-based printing ink eliminates dependance on petroleum products and provides competitive performance characteristics.
According to the present invention, vegetable oil-based printing inks are provided which can be produced in a wide range of viscosities while lowering costs and recycling ink waste. The vegetable oil-based printing inks of the present invention are produced by admixing colorant with a vegetable-oil based printing ink vehicle (hereinafter xe2x80x9cvehiclexe2x80x9d). The vehicle comprises a polymerized vegetable oil and may comprise an unpolymerized vegetable oil produced by admixing from about 5 to about 100 weight percent of polymerized vegetable oil and from 0 to about 95 weight percent unpolymerized vegetable oil sufficient to achieve a viscosity of at least 20 poises.
The vegetable oil-based printing ink may be reclaimed directly from the printing press by applying unpolymerized vegetable oil to the printing press to dissolve residual vegetable oil-based printing ink thereby removing the residual vegetable oil-based printing ink from the printing press and forming a contaminated printing ink. The contaminated printing ink is filtered to remove particulate matter thereby yielding a substantially particulate free residual printing ink. The substantially particulate free residual printing ink is then admixed with an effective amount of colorant and an effective amount of fresh vegetable oil based printing ink vehicle to provide a vegetable oil-based printing ink with at least about 20 poises and a predetermined color.
The polymerized vegetable oil having a viscosity of at least about 20 poises employed in the vegetable oil-based ink vehicle is produced by polymerizing vegetable oil in an evacuated steady state or continuous flow reactor system. More specifically, polymerization of the unpolymerized vegetable oil is achieved by heating unpolymerized vegetable oil under vacuum, to a temperature of from about 150 to about 210 degrees C. for a period of time effective to provide a substantially oxygen free unpolymerized vegetable oil. The substantially oxygen free unpolymerized vegetable oil is then heated under vacuum to a temperature of from about 280 to about 330 degrees C. for a period of time effective to provide a substantially colorless polymerized vegetable oil having a viscosity of at least about 20 poises.
An object of the present invention is to provide vegetable oil-based printing inks having a viscosity of at least 20 poises adaptable for use with a wide variety of printing presses.
Another object of the invention, while achieving the before-stated objective, is to provide a method of reclaiming residual vegetable oil-based printing ink from printing presses.
Yet another object of the present invention, while achieving the before-stated objectives, is to provide a method of cleaning a printing press wherein the waste cleaning solution is biodegradable and thereby substantially reduces the environmental impact of disposal of the waste.
Another object of the invention, while achieving the before-stated objectives, is to provide a method for polymerizing vegetable oil having a wide range of viscosities.
Other objects, advantages, and features of the present invention will become obvious to those skilled in the art upon reading the following detailed description.